1. Field of the Invention
The present invention relates to a method used in a wireless communication system and related communication device, and more particularly, to a method of handling an interference mitigation and related communication device.
2. Description of the Prior Art
A long-term evolution (LTE) system supporting the 3rd Generation Partnership Project (3GPP) Rel-8 standard and/or the 3GPP Rel-9 standard are developed by the 3GPP as a successor of a universal mobile telecommunications system (UMTS), for further enhancing performance of the UMTS to satisfy increasing needs of users. The LTE system includes a new radio interface and a new radio network architecture that provides a high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, a radio access network known as an evolved universal terrestrial radio access network (E-UTRAN) includes multiple evolved Node-Bs (eNBs) for communicating with multiple user equipments (UEs), and for communicating with a core network including a mobility management entity (MME), a serving gateway, etc., for Non-Access Stratum (NAS) control.
A LTE-advanced (LTE-A) system, as its name implies, is an evolution of the LTE system. The LTE-A system targets faster switching between power states, improves performance at the coverage edge of an eNB, and includes advanced techniques, such as carrier aggregation (CA), coordinated multipoint (COMP) transmission/reception, uplink multiple-input multiple-output (UL-MIMO), etc. For a UE and an eNB to communicate with each other in the LTE-A system, the UE and the eNB must support standards developed for the LTE-A system, such as the 3GPP Rel-10 standard or later versions.
Different from the LTE/LTE-A system operating in a frequency-division duplexing (FDD) mode, transmission directions of subframes of a frequency band in the LTE/LTE-A system operating in a time-division duplexing (TDD) mode may be different. That is, the subframes in the same frequency band are divided into UL subframes, downlink (DL) subframes and special subframes according to the UL/DL configuration specified in the 3GPP standard.
Please refer to FIG. 1 which is a table 10 of the UL/DL configuration with subframes and corresponding transmission directions. In FIG. 1, 7 UL/DL configurations are shown, wherein each of the UL/DL configurations indicates a set of transmission directions for 10 subframes, respectively. In detail, “U” means that the subframe is a UL subframe where UL data is transmitted, and “D” means that the subframe is a DL subframe where DL data is transmitted. “S” means that the subframe is a special subframe where control information and may be data (according to a configuration of the special subframe) is transmitted.
However, eNBs in the LTE/LTE-A system operating in the TDD mode (hereinafter, the TDD system, for short) may be configured with various UL/DL configurations. In other words, a DL subframe for an eNB may be UL subframes for neighboring eNBs of the eNB, when the eNB and the neighboring eNBs are configured with different UL/DL configurations. In another example, a UL subframe for the eNB may be DL subframes for the neighboring eNBs of the eNB. In this situation, various combinations of interferences may be caused to the eNB or the UE. For example, the eNB may be interfered by interferences caused by UL transmissions and/or DL transmissions in a subframe performed by neighboring eNBs, when the eNB performs a DL transmission in the subframe to the UE. Throughputs of the eNB and the UE may be degraded due to the interferences.
Thus, it is important to mitigate the interferences caused to the eNB and the UE. Interference mitigation in the TDD system becomes an important problem to be solved.